Centrifugal pumps are used for pumping pump media, which in general are fluids. The pump media enters the centrifugal pump through the inlet and is pumped through the rotation of the impeller to the pressure side and is output under pressure through the outlet. In many cases, the outlet is located radially with regard to the impeller, wherein a radial flow is generated by the impeller.
For a good efficiency of the pumps, sufficient sealing is required between the pressure side and the suction side. For this purpose, the impeller interacts with an impeller seat that is formed stationarily in the pump housing. In order to enable a movement of the impeller relative to the impeller seat, a sealing as complete as possible between the impeller and the impeller seat requires accurately fitting fabrication and, if necessary, additional sealing. This makes the production of the pump complicated and expensive.
Due to unavoidable manufacturing tolerances, unpleasant grinding noises can be heard which stop only after a certain running-in time. These grinding noises result from contact between the impeller and the impeller seat and cause material abrasion at least on one of these two elements. However, this results also in bypass connections, thus leaks, between the suction side and the pressure side. Also, replacing the impeller is relatively problematic since usually the new impeller does not correspond to the shape of the old impeller seat.
This can also result in damage to a coating of the pump housing or the impeller seat. This is in particular problematic if the centrifugal pump is used for corrosive fluids such as, for example, swimming pool water. After long downtimes, in the worst case, rust-induced seizing up of the impeller in the impeller seat can occur, which entails significant maintenance work or even requires complete replacement of the pump.